What is this

[lewis121]

Whatever this is takes over my tank 2 days after every clean I only have 1 fish and 3 shrimps tanks been going about 8 months this has been happening for about 2 months

 

[Andy Sager]

It's brown diatoms which are common in newer tanks. Since you say it's happening after a water change, I'd check your tap water for phosphates as this is usually the cause of brown diatoms. The good news is that it's not something dangerous to the fish or shrimp and they will usually go away on their own as the tank matures HOWEVER, if the problem is your tap water, you'd be wise to use a different water source to replace your water with so you don't keep feeding the problem or another option would be to use a phosphate absorbing product in your filter to help keep the level low. The bad news is that can be unsightly to look at.

Hope this helps.